This application relates to a refrigerant system wherein a motor for at least one component in a refrigerant system is provided with a variable frequency control, and a ratio of the frequency to voltage provided by this control is adjusted to be at an optimum level.
Refrigerant systems are utilized in many air conditioning and heat pump applications for cooling and/or heating the air entering an environment. The cooling or heating load on the environment may vary with ambient conditions, and as the temperature and/or humidity levels demanded by an occupant of the environment change.
In some refrigerant systems, a single compressor is utilized to compress the refrigerant and move the refrigerant through the cycle connecting indoor and outdoor heat exchangers in a closed loop. However, under many circumstances, it would be desirable to have the ability to vary the capacity, or amount of cooling or heating provided by the refrigerant system.
Variable speed drives are known for driving compressors at a variable speed in a refrigerant system. By driving the compressor at a higher or lower speed, the amount of refrigerant that is compressed per unit of time changes, and thus the system capacity can be adjusted. Other refrigerant system components such as fans and pumps may be provided with variable speed drives as well for similar purposes of enhanced performance, improved reliability and operational safety.
In general, known variable frequency controls have been operated such that a ratio of the voltage to the frequency is maintained constant. Thus, as the frequency increases, so does the voltage. On the other hand, modern inverters within these variable speed controls have the ability to adjust both frequency and voltage independently of each other. Thus, the limitation in the prior art of maintaining the constant voltage-to-frequency ratio is not necessary.
The present invention seeks to improve performance of these known systems by optimizing the voltage-to-frequency ratio dependent on system operating and environmental conditions.